C++ Primer Plus

C++ programmers are blessed (or cursed) with myriad options when naming functions, classes, and variables. Programmers have strong and varied opinions about style, and these often surface as holy wars in public forums. Starting with the same basic idea for a function name, a programmer might select any of the following:

MyFunction( )

myfunction( )

myFunction( )

my_function( )

my_funct( )

The choice will depend on the development team, the idiosyncrasies of the technologies or libraries used, and the tastes and preferences of the individual programmer. Rest assured that any style consistent with the C++ rules presented in Chapter 3 is correct as far as the C++ language is concerned, and it can be used based on your own judgment.

Language allowances aside, it is worth noting that a personal naming style—one that aids you through consistency and precision—is well worth pursuing. A precise, recognizable personal naming convention is a hallmark of good software engineering, and it will aid you throughout your programming career.

Summary

A C++ program consists of one or more modules called functions. Programs begin executing at the beginning of the function called main() (all lowercase), so you should always have a function by this name. A function, in turn, consists of a header and a body. The function header tells you what kind of return value, if any, the function produces and what sort of information it expects arguments to pass to it. The function body consists of a series of C++ statements enclosed in paired braces ({}).

C++ statement types include the following:

• Declaration statement— A declaration statement announces the name and the type of a variable used in a function.

• Assignment statement— An assignment statement uses the assignment operator (=) to assign a value to a variable.

• Message statement— A message statement sends a message to an object, initiating some sort of action.

• Function call— A function call activates a function. When the called function terminates, the program returns to the statement in the calling function immediately following the function call.

• Function prototype— A function prototype declares the return type for a function, along with the number and type of arguments the function expects.

• Return statement— A return statement sends a value from a called function back to the calling function.

A class is a user-defined specification for a data type. This specification details how information is to be represented and also the operations that can be performed with the data. An object is an entity created according to a class prescription, just as a simple variable is an entity created according to a data type description.

C++ provides two predefined objects (cin and cout) for handling input and output. They are examples of the istream and ostream classes, which are defined in the iostream file. These classes view input and output as streams of characters. The insertion operator (<<), which is defined for the ostream class, lets you insert data into the output stream, and the extraction operator (>>), which is defined for the istream class, lets you extract information from the input stream. Both cin and cout are smart objects, capable of automatically converting information from one form to another according to the program context.

C++ can use the extensive set of C library functions. To use a library function, you should include the header file that provides the prototype for the function.

Now that you have an overall view of simple C++ programs, you can go on in the next chapters to fill in details and expand horizons.

Chapter Review

You can find the answers to the chapter review at the end of each chapter in Appendix J, “Answers to Chapter Review.”

1. What are the modules of C++ programs called?

2. What does the following preprocessor directive do?

#include

3. What does the following statement do?

using namespace std;

4. What statement would you use to print the phrase “Hello, world” and then start a new line?

5. What statement would you use to create an integer variable with the name cheeses?

6. What statement would you use to assign the value 32 to the variable cheeses?

7. What statement would you use to read a value from keyboard input into the variable cheeses?

8. What statement would you use to print “We have X varieties of cheese,” where the current value of the cheeses variable replaces X?

9. What do the following function prototypes tell you about the functions?

int froop(double t);

void rattle(int n);

int prune(void);

10. When do you not have to use the keyword return when you define a function?

11. Suppose your main() function has the following line:

cout << "Please enter your PIN: ";

And suppose the compiler complains that cout is an unknown identifier. What is the likely cause of this complaint, and what are three ways to fix the problem?